From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-1468877-1518324554-2-415304867367568087 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.001, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='US', FromHeader='uk', MailFrom='org' X-Spam-charsets: cc='UTF-8', plain='UTF-8' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1518324554; b=QtLcH+FVBrCMX2bhQ/DssR/5JWBVP6veTlSzHu5qDVdTRTR jQAsmaeyirKfGeIUNj7JmXbMJsBppJOciqdDmR2HD5k2SGVtw6NyuC2+F4q+t0fe FdXIPSNiBkjCsCff0RFjBI+G6xpkGrzOXYVnQ7tQl1tevmwQ5oHeZUCuGqvQ0hPX o5YW5kJFTrJ+n6uJbPjS9XwZa6EWNosqQWcJd91bCdABngL67doSg1Q1f8QSz9aC +9C78CxGMh34+ECU0TmpdKs1DoV6DUStMY+OULuRohkwZxvyPin6TBd6vK72noYe 6kFvNPu5HaWaOhmRTiokwXF2z/tUxnRDUrOt67Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=content-type:content-transfer-encoding :mime-version:from:to:cc:date:message-id:subject:in-reply-to :sender:list-id; s=arctest; t=1518324554; bh=gwo2YePGMhVJASC2iAw HZnmMzlSIjGzMW0Dld4r5gGI=; b=h0rU/UOmXzmeZFiGyl5ixF6joj2qnIPYgtU VRyGWFGoGQQVxHxnZCxwenugRZjck3Op42lz83u7YVzGdNTMQxzhcsSgnNG0UsKZ b676hveNfFO7LfeFQ+VU0SaZPEw4+HWhOD4dMzO/1EGK8jReaYr8aHR89dFU0mR7 epF09xj0kPPvmy4eyMUH+v2qjtn+G7gdgTBUJGQdYNLeFVKZ4vq2mRKlcEQmY17N qvAJRXETqN7jP9f9n5ulYBXFpPqlpRFzxwhD4ch78UG7QvqneYJ9xvEPTcvxvKBV ZqcxxWYOLwZTm4zwEQCmeLuge6M5ZTbWRN2AkPpDvCQ4zoaMo3w== ARC-Authentication-Results: i=1; mx3.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=decadent.org.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=decadent.org.uk header.result=pass header_is_org_domain=yes Authentication-Results: mx3.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=decadent.org.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=decadent.org.uk header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753407AbeBKErw (ORCPT ); Sat, 10 Feb 2018 23:47:52 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:41816 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752840AbeBKEd6 (ORCPT ); Sat, 10 Feb 2018 23:33:58 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "David Hildenbrand" , "Radim =?UTF-8?Q?Kr=C4=8Dm=C3=A1=C5=99?=" , "Paolo Bonzini" , "Nick Sarnie" Date: Sun, 11 Feb 2018 04:31:11 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 089/136] KVM: SVM: obey guest PAT In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 3.16.54-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Paolo Bonzini commit 15038e14724799b8c205beb5f20f9e54896013c3 upstream. For many years some users of assigned devices have reported worse performance on AMD processors with NPT than on AMD without NPT, Intel or bare metal. The reason turned out to be that SVM is discarding the guest PAT setting and uses the default (PA0=PA4=WB, PA1=PA5=WT, PA2=PA6=UC-, PA3=UC). The guest might be using a different setting, and especially might want write combining but isn't getting it (instead getting slow UC or UC- accesses). Thanks a lot to geoff@hostfission.com for noticing the relation to the g_pat setting. The patch has been tested also by a bunch of people on VFIO users forums. Fixes: 709ddebf81cb40e3c36c6109a7892e8b93a09464 Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=196409 Signed-off-by: Paolo Bonzini Reviewed-by: David Hildenbrand Tested-by: Nick Sarnie Signed-off-by: Radim Krčmář Signed-off-by: Ben Hutchings --- arch/x86/kvm/svm.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -3157,6 +3157,13 @@ static int svm_set_msr(struct kvm_vcpu * u32 ecx = msr->index; u64 data = msr->data; switch (ecx) { + case MSR_IA32_CR_PAT: + if (!kvm_mtrr_valid(vcpu, MSR_IA32_CR_PAT, data)) + return 1; + vcpu->arch.pat = data; + svm->vmcb->save.g_pat = data; + mark_dirty(svm->vmcb, VMCB_NPT); + break; case MSR_IA32_TSC: kvm_write_tsc(vcpu, msr); break;